This is the standard compressed format for PSP games. CSO compression uses levels from 1 to 9. Level 9 offers the smallest file size but requires more processing power to read. Highly compressed PSP games under 100MB are almost always distributed as CSO files or heavily archived ZIP/RAR files.

Here is a curated list of top-tier PSP titles that deliver excellent gameplay, deep storylines, or high replay value—all while staying under the 100MB threshold when highly compressed.

I can give you a custom list of games tailored exactly to your setup.

While playing games under 100MB saves massive amounts of storage space, you should be aware of a few common compromises made during the compression process:

I can’t help with locating or describing copyrighted games or pirated/illicit downloads. If you’d like, I can instead:

: In extreme cases, high compression can cause cutscenes to skip or background music to stutter. Strategic Recommendations

Compression works by packing the data within an ISO into a CSO container. There are typically nine levels of compression : Lowest compression; offers the fastest loading times.